Process for the manufacture of aluminium nitrid.



P. BUNET.

PROCESS FOR THE MNUFACTURE 0F ALUWHNIUM NITRiD. APPUCATION min MAY 9, i913,

1..,145'47 Patented 6,1915.

P: BUNET.

PROCESS FOR THE MANUFACTURE of ALUMIMUM NxTRlD,

APPUCATION FILED MAYS, 1913.

Patented July 6 2 SHEETSf-SHEE PATENT @Flllil F JHXTNF-Y, NORTH CAROLINA, ASSIGNOR TO SOCE'T QENEELE 15315;

NI'RUEES, Ol' PARS, FRANCE.

EOE?, THE LJANYLTIACTURE OF ALUMINEUEE' NITRID.

Speccation of Letters Patent. Pgignfgd Jule tion 'iicd lfay 9, 1913. Scial N0. 766,461.

These two types of furnace can` evidenti o BDNF/r, of be combined. i eren Carolina, The accompanying drawing shows by n e republic or -France, of examples various forms of construct 1 in new and useful Inn of furnaces for carrying out the process. ce

for the lvanufac- Figure l is a longitudinal section, illusld, of which the foltrating an inclined revolvingr electric fu ,and enact description. nace, according to my invention; Fig. i relates to a process for the a vertical section of a stationary 'orin c uminiurs nitrid ley the furnace; Figs. 3 and 4 are diagramme ic in heating in pressections oi' two modified forms of revolving o` of gases containing 'the electric furnaces.

l of aluA or alumincus Fig. l shows a revolving furnace, which roon ir au electrical r is slight-ly inclined so as to allow the suliaco in X:fini/:la material under stances introduced into the furnace to rues the, heating reif'ance therethrough in a continuousznanner,

lafter the general manner described in the mention consists in effecting the ad- Serpek Patent, No. 1,030,929, July 2', 19 2. coi nuous electrical furnace The gaseous current.containing nitrogen cirse above substances roonculates' as usual, in the contrary direction to es or other conthe 'materials The electric current is l i nt quantity to to two annular conductors A and B ci Win currene in spite of the the lower one B projects inside the farm carocw7 necessary to so as to `torni a diaphragm and to retain th of c le alumina into 'material C traveling through the furnace, eo-

s explained above, in proportion as the alie placerin elecmaterial advances through the furnace and nd, which the rnathe transformation into nitrid becomes more itself Serres. aa the complete, the thickness of the layeris in- A is, however, Carried creased, in this Way allowing of .maintaine n one or other of the types ing at every cross section the quantity of ereater described. carbon sufficient to insure the regular pasl @me :if furnace is arranged in sage of the current in spite of the losses ref that the thickness or 'the layer Sultin'g from the reaction. Watters 35 of material goes on increasing in proportherefore, be so arranged that the resistance 9o tion as the latter advances ti rough the furand consequently the evolution of heat are nar in i "he sectional area in. approximately constant throughout the the furnace where the length of thc furnace. En order to heat u i poor in carbon in eonsethe furnace and to facilitato the il O 1 'lor and there is, therethe current at the start, the operai; i al e5 ss-seetion of the be commenced by passing carbon alone ci conductive through the furnace; the mixture to i passage of the teatcdh'is then gradually added. There ma l be arranged in the* furnace at certain 'inten 'YQc of furnaceisso arranged Vals conductive rings D ittedin the rerco s along its length there are fractory lining, E, and prfqccting or not. eleclrod for conveying the In this Way there are formed iu the furnn "e ed alternatelgT to Zones of less resistance which ia ".tatc or supply. En passage ot' the current. This arrangerner is divided into a numallows the furnace to be made of any lengthE ions through which greater in proportion to the size of the protreatment passes succesjections of the conductive rings D.

" section can "ce Fig. or' the drawinge=shows a atelier-err state o' een to the two electrodes A1 andl B1. The material poured upon the side of the electrode A1 falls upon the lateralwalls of the furnace forming 'a' slop'mgbank, the sectional area of which increases toward the lower electrode B1. The electrode A1 is insulated on its underside by'an insulating support A2 in order that the lcurrent shall ass with certainty through the mixture 1 under treatment. The electrode A1 and -its supl port A2 are movable and can' be raised or lowered; in this way the' furnace is 'regulated by increasing or decreasmg the sepai ration of the electrodes and the areas for Vns Ithe'passage ofv the mixture. closedl by plugs. F1,fare formed atv the .bottom of the furnace at various 'points in the periphery to allowfthe materialto be withdrawn. v

Fig. 3 is a lon '.tudinal section of a furnace of the'scconl type, in' which an intermediate electrode or terminal B3' is arranged between the extreme electrodes'A3, A, all these electrodes being'formed as conductive 25 rings or annuli.

Fig. 4 is a longitudinal section' of a. similar furnace, having two intermediate electrodes; in this case some of the conductive rings forming terminals have been arranged to project internally of the furnace so as to afford walls or diaphragms according to the principle of the first type of furnace above described.'

In the arrangement of Fig. 4, the conductive rings A3, A4 are connected to oneof the poles of the electrical generator while the alternate rings B8, B1 are connected to' .thecther pole.

In these two figures, E still indicates` the refractory liningV of the furnace and C the material in course of its advance therethrough. The current of nitrogen circulates in the opposite direction as usual.

The use of intermediate electrodes-and the possibility of selecting their separation asl desired, form a practical method which. allows latitude for regulating in accordance .with the requirement of manufacture one or more of the following factors which are all of importance in the management of revolving electrical furnaces, vizz-voltage, resistance, current intensity, length and inclination of the furnace, proportion of the conductive material added to the mass in reaction, total expenditure of energy( and of heat and division of the matter along theI various elementary sections of the furnace.

In particular, by/reducing the length of the path traveled by the material between two successive electrodes, the resistance is diminished. It becomes possible,.therefore, to reduce the quantity of conducting material added to the materials in reaction in order to insure the passage of the current; this allows of diminishing. the expenditure Openings F,

`sty of the` current, and, therefore',ofl 'quantity of Aheatwhich passes through-the Yis necessary to the reaction." A partierthe' 4of energy devoted 'to the heating/of` these ,conductlvematerials and to obtain at--the' .end of the operation a product which is not surcharged with inert material and is, there'- fore, richer in nitrid. Instead of lreducing the proportion 'of conductive matter added, ,thelength of the' furnace may be increased without reachinga resistancerdeleterious to. the satisfactory carrying out of the operation. In this way there is obtained a Vref sult analogous to'that' which is" produced by the conductivdrings D, whichare 4not connected to the poles of thefgenerator in -the furnace shown in Fig. 1, Again, byV

bringing closer together two-consecutive '8o-v electrodes, the heat may be concentrated in 'y a given zone as' desired, for exampleinthe final zone which is the oorest 1n carbon and in which the curren hasv most diliicultyj Y nace, which presents an important advantage, lies inqthe fact that-it antoniatlcally Vthe regulation of tha'inte'n different elementar'ysections ofthe urnaceg' Indeed, if forany reason the intensity off the current increased abnormally atene of-f the sections of thel furnace, to the detriment-1f of the others, there wouldbe reduced-a that point a larger quantity o 'heat'; thisv would increase the reaction of-the carbon.;

' rangement is illustratedin Fig. 4., In this 'l way it ,becomes possible to combine the. use ful effects of the methods ofregulation! the two systems, according to dnerent re 4 quirements. In particular, it becomes'posfjL-J.V sible to va as desired in eachelementary section of' t e furnace, the thickness of the 1 ylayer of material under treatment, andthe extent which it occupies between two consecutive eLctrodes.

As stated above, the material delivered to the furnace vmay be a mixture ,of alumina' and carbonwith an excess ofthe. latter over or above the quantity necessary tothe ite-' j. action. By waybf exam le, itmay bestated that there may be intro uced into the ture a quantity of carbon double'that which whole `of this excess of carbon may^ how ever, equally well be replaced b y lo 1 'I' e 'o1"'-' more substances which are goodf'lectrlal iso l i. insisting meme? conductors, die metals for exempie. Among these substancesi i'u is of edvun'age o select those which possess ai; the seme `ime the propery of acti #ie resetion ferme-- tion of nitrid. One may, for example, use iron, ooppel nickel, manganese er iieir ores or sgsiii aiioys of these iiietais, such as ierzo-Riolo/i ferrdsiiicem ferro-manganese, etc. The use of iron or of eert-ain of iis zdlogre has the further spef'ii advantage of silawieg it to be se minted magnetically from the aluminium riiird :it theend of the operaion.

Since iron o id already .found in greater Gr iess propel Liens in Certain eiumniui'n ores, fin 'parieulur the ,ii'errugiiious bmiiies, for example)` it will suileiemb iii case of die ilse of ores to comple@ by additions the qusiitiy of iron required to obtain the deired Conductivity of the mass under rea meni". A

The maerial introduced into the furnace (Whatever be its Composition and Whatever be the ype of ferri-ce empioyed) 'may be in 'ie puiveruien state or in the form of aggiomerees; it may again be in the form of aggiomerates ooiiainiiig only the alumina.. or edmninous material and me carbon neces sary se the reaction, wiiiie the Carbon or nher eeiiductive materie-.i intended to insure the desired Conductivity is added separati-dy. In Case the conductive materiel added con- Whoiiy or in pari' ef Carbon, the etinospiiei'ie air may 'oe used directiy as il ges of the reaction; the excess of carbon c011- tziiiied in the maerizd may hen serve at "die end of the operation and beyond the eiec tricai zone te deprive this sir of its exygen.

in carrying out my above [i prec ess of mf nufneturiiig eiumiiium iiiiid, de

not res s t myseif to the use of the construe tion of lunace described. The Const-'rueapp icaiion.

Claim as my invention:

As en improx'emeiit in the process fer the manufacture of lioiiufi nirid by prf-sei ee of nir'ngen e mitici e of mseiiai mid esrbom ie proc iii- Causing e advance in s coninueus eiectrieal iu ace ie mixture of ie sctifiiiiary materiais mili sii addition of Conf ducive mziteiiais which at the same time actif); the reaction.

Q. As an improvement in the process for iie limoni-Cime of aiuminium nitrid by heeing in presenze of nitrogen a mixture of uiimiiieus materialand carbon, the process consisting in causing e advance in a oontnuous electrical furnace the mixture of reawienary mite isis Wih an addition of conductive nl, Jriei, .which ac ies die reacion und is also ambie magneticsiiy at die end of the epi vmon. i

3. is se improvement in die process iieatig in ziimunous for the hes siemiiieus consisting inuois eie cases ssznnding the heating in pres duiiiiiious Censis@ ie Cue 11 Timone e eeried zietionarj i duc'tizfe feiiu* new *Lib szmdiiig iie lessi reaeiois, Jdie layer of :c the ouiet. as described s an ref-eme i? aiumnous i son, the process consisiiig g advenee iii :L C 2;* tinuous eis@ mi furnace the mixture of reactionary maierisis with im M i l ne" air to the excess of @arbor and suppl;

furnace the Avery end., iieiebj/ providmg gas con T i reeioff of the excess eris 5. heating ina-tee energy, which eens C' in zi rotary femmes havin"r ii 'Ming iiiiigj i charge of hij ne se iie ii roaciiig the furnace.

y 1 v P 1 S. 1 he herelri described memo@ or nesting v graneiar noli-eendueiiig maerieis means O eiecrics! iisiiiiig in roizai f insuieiing lining eoiidizeiiig msterii ing current through the charge while' rotating the furnace, and supplying granular non-conductingmaterial to one end of the furnace and withdrawing such material from the other end while retaining inside the furnace the said lumps or masses of conducting material. y 9.` The herein described method of heating non-conducting aluminiferous thepresence of gaseous mtrogen for the production of aluminum nitrid, `which consistsv in establishing in a rotary furnace having a highly insulating and refractory lining a material in Witnesses WALTER ABBE, HUBERT HOWEN, 

